Method of determining melting-points.



L. W. CHUBB & R. DE 8. BROWN. METHOD OF DETERMINING MELTING POINTS.

APPLICATION HLED MAY 6.1915.

Patented Jan. 14, 1919.

INVENTOR Lew/5n! C/mbb & fFgbs'o/ De 5 Brawn.

WITNESSES ATTORNEY To all whom; amt-06mm.- I

UNITED STATES PATENT OFFICE.

mwIsw'. cause, or 'EnGEwoon A K 'ND noBsfoN DE BROWN, 0 w tK NsBuEe,

PENNSYLVANIA, ASSIGNORS TO WESTINGHOUSE ELEcTn c A DM UEACTUEINcolumn-2,1 coEronArIo or PENNSYLVANIA.

' METHOD or DETERMI ING I Be it known that we, LEWIS .W. CHUBE, a

.citizen of the United States, and a resident of Edgewood Park, in thecounty of Allegheny and State of Pennsylvania, and RonsoN DE S. BROWN, acitizen of the United States, and a resident of Wilkinsburg, .in thecounty of Allegheny and State of Pennsylvania, have invented a new anduseful Improvement in Methods of Determining Meltlug-Points, of whichthe followlng 1s a specification.

Our invention relates to methods and apparatus for determining meltingpoints, and it has for one of its objects to provide a rapid andaccurate method of determining the melting points of solid bodieswithout the necessity of visually observing the change of form of suchbodies when they pass from the solid to the liquid state.

Another object of our invention is to provide convenient apparatus forpractising the foregoing process.-

In the accompanying drawing, Figure 1 is a diagrammatic view showing asystem arranged for the determination of melting points according to ourprocess. Fig. 2 is a diagrammatic view showing another arrangement ofapparatus for carrying out the same process. Fig. 3 is a diagrammaticview showing a further modification of part of the apparatus employed.Fig. l'is a vertical sectional view of a thermo-couple provided with asuitable holder, and Fig. 5 is a' diagrammatic view showing a stillfurther modification of suitable apparatus.

In a copending. application for Letters Patent of. Lewis W. Chubb,Serial No. 26,322, filed May 6, 1915, a system for determining meltingpoints is described, in which a particleof the material tobe tested is"plac'edupon a thermo-couple formed, for example, of a platinum supportto which is I electro-percussively welded; or: otherwise intimatelyattached, a rhodium or platinum rhodium wire. electrically heated bypassing alternating current through it, 'andthe melting point isdetermined by visually observing the particl througlh asui'tablemicroscope, noting the instant w en it changes its 'form'and begins tofuse together, and, at that instant, observing the readingof adirect'current elecspecification of Letters Patent. Application med Maya, 19 15 :SerialNo. 26,321.

The platinum' 'support is' M L'rINc-roINrrs.

ratenteaaaniie, 1.919.

trical measuring instrument inserted-in circuit with the thermo-electrocouple. 7

According to our present invention, we dispense withthe visualobservation of the material being tested and thereby increase theaccuracy of the determination, since the observer may easily fail toobserve the change of form ofthe test particle for an appreciable time,and the personal equation of the observer must be taken into account inmaking very accurate determinations.

.Our method consists, in general, in melting the material to be testedin, contact with a thermo-electric couple, the terminals of which areconnected to a direct-current measuringinstrument, such as apotentiometer or a millivoltmeter and observingthe readings of theinstrument as, the temperature of the couple rises. At the instant whenthematerial adjacent to the thermoto the liquid couple passes from thesolid its latent heat state, the material will absorb of fusion, and thetemperature of thether 1 mo-couple will remain nearly stationary for anappreciable time, or may even decrease, notwithstanding the constantincrease in the heat applied "to it. This pause in the'rise oftemperature will efi'ect a corresponding pause in the rate of increaseof the potential generated by the thermo-couple, which will cause acorresponding variation in the reading of the measuring instrument. Thein strument will, therefore, by this pause in the movement of itsindicator, show the exact potential generated by the thermo-couple at 1the instant when the material fuses, and the temperature may be computedfrom thisv reading by ordinary methods.

The point at which the instrument indicator pauses may be detected bymerely observing the instrument and noting? thespoint at whichthesteadyadvance: of the indicator is temporarily interrupted moreaccurate method, however, is to take successive readings'at equalintervals ia few seconds apart, and-to-plota curve in which, for =eX-ample, the ordinates-represent time and'the abscissas are fractions ofmillivolt s." The curve will rise regularly, as, thetemper'ature rises,until the material reacheswitsmelting point, when the curve'will'breaksharply and then resume its original direction after the lapseof-several observation period'sfl by means of 20 of conductors '10 and 11,

40 is su plied to 45 in Fig. 2, .two wires to tion point of t e wires 17and so are cmnectcd,

The foregoing process may be practised numerous difi'erent arrangementsof circuits and apparatus, some of which are illustrated in theaccompanying 6 drawing. In Fig. 1, a test sample 1 is supported upon aflat support 2 of platinum or other refractory conducting material, towhich is electro-percussively welded, or otherwise suitably attached, arod or wire 3 10. ,whichmay be of rhodium or platinum-rhodium alloy.This arrangement of parts is similar to that shown in the copendingapplication above referred to, and may be similarly connected to lineconductors 4 and 5 energized from a suitable source of alternatmgcurrent. Connection is made to the support 2 from the conductors 4 and 5by means of supply conductors 6, 7 8 and 9, and the conductors 7 and 8are connected, by means to a non-inductive resistance element 12. Themember 3 of the thermo-electric couple is connected, by means of aconductor 13, to the neutral point 14 or point 80 which may be amillivoltmeter, is inserted in circuit in the conductor 13, and analternating-current measuring. instrument 16 may also be inserted incircuit in the conductor 13 for the purpose of bringing the terminal 85of the conductor 13 to the neutral point of the resistance element 12.In determining melting points sample 1 is ,placed at the junction pointof the members 2 and- 3. Alternating current the line conductors 4 and5, andt e instrument 15 is read at equal intervals in the mannerdescribed above.

Figs. 2, 3 .and 5 show modified forms of thermocouples. In thearrangement shown 17 and 18, of difl'erent conducting materials, arecrossed and welded'together or otherwise united, forming athermo-electricvcouple. The material to be tested is brou ht intocontact with thejunc- 18, which may be done by embedding this junctionpoint in the material to be tested or pressing a,

' portion ofthematerial around the junction if itis a plastic substance.The terminals 55 19 9.115120 ofsthe .wires 17 and 18 are respectivelyconnected to line conductors 21 and 22 that are energized ,from asuitable source of alternating current, while the opposite tcrminals.23and 2A f the wires 17 and 18 p by means of conductors 25 and 26, to adirect-current measuring in- .strument27, eit er;a,potentiometer or amillivoltmeter." Determinations are made with this device in the mannerdescribed above.

66 :3 showsamodified device, in which of no alternating current flow I25 of the non-inductive resistance element 12,

. handle in a cord 40.

by means of thissystem, the

the thermo-couple is hon 28 formed by percussively welding the a smallflat sheet or rib ends of two rods of difi'erent materials tothe weldedrods into a gether, rolling out thin sheet and cutting out asmallportion The as shown, is advantageous" including parts of bothmaterials. notched outline, because it localizes the heat at thejunction point between the two unlikemetals. Alternating current forheatingthe couple is supplied from line conductors 29 and 30, throughsupply conductors 3L and 32' which are attached'to opposite points ofthe ther- -mo-couple 28. The opposite members 33 and 34 of thethermo-couple consist, as stated, of difi'erent conducting materials,and are connected, by conductors-35 and 36, to a direct-currentmeasuring instrument 37 by means of which determinations are made, asalready described. This form of thermocouple is particularly convenientwhen mounted in a holder, such as that shown in Fig. 4, in which thethermo-couple 28 is backed with feltmr other suitable heat-insulatingmaterial 38 and is attached. to a' suitable handle 39. The necessaryelectrical connections are provided and led from-the By means of thisdevice, the thermo-couple may be placed fiatagainst the side of a massof any material, the melting point of .which is to be determined, andthe melting point ascertained very quickly and with great'precision bymeans of the direct-current measuring instrument.

Another form of thermo-couple' that is illustrated in Fig. 5, consistsof two ribbons or plates and 42 of unlike conducting materials,spot-welded together along the line 43 and bent into the form shown. The

electrical connections are similar to those shown in Fig. 2, alternatingcurrent for heating the couple being supplied from line conductors 44and 45 to two unlike leaves of the thermo-couplc, while the two remainmgleaves are connected, by means of conductors 46 and 47,toa measuringinstrument 48. This form of thermo-couple is particularly useful indetermining the melting points of soft materials into which the couplemay be thrust edgewis, a suitable handle (not shown) being provided forthis purpose.

The foregoing apparatus has been shown and described by way ofillustrating the numerous ways in which our invention may be practised,and it is to be understood that our invention comprehends all suchmodifications and adaptations as fall within the see e of the appendedclaims.

e' c as our invention:

1. The method of determining melting points that consists in placing thematerial to be tested in engagement with 'a thermocouple, heatingthe cuple by. regularly ,in-

5 the potential tric couple,

creasing increments and observing the value of the potential generatedby the couple at the poin,t at which the progressive increase 111. thegenerated potential is interrupted by reasonof the absorption of heat atthe melting point by the material being tested.

2/ The method of determining melting points that comprises placing thematerial to be tested in contact with a thermoelecheating .thersaidcouple, by regular and progressive increments, and reading upon a directcurrent measuring instrument associated with the said couple the pointat which the progressive increase in generated by the aid couple is,interrupted by reason of the absorption of heat at the melting point bythe material being tested.

3. The method of determining melting points that comprises placing thematerial to be tested in contact with a thermo-electric couple, rentthrough the said couple to raise its temperature, by regular andprogressive increments, to the melting point of the said material, andperiodically observing a direct current measuring instrument, soassociated with the said couple as to measure the potential generatedthereby,as the temperature of the said couple is raised.

4. A device for determining melting points that comprises athermo-electric cou ple consistin of two, crossed and united bodies ofdifferent conducting materials, means for supplying electric current totwo unlike arms of the said pouple, and an electrical measuringinstrument connected in circuit with the other two arms of the saidcouple.

two unlike passing alternating electric cur- 5. A device for determiningmelting points that. comprises a thermo-electric couple consisting oftwo crossed and united bodies of different conducting materials, meansfor supplying alternating electric current to arms of the said couple,and a direct current measuring instrument connected in circuit with theother two arms of the said couple.

6. A device for determining melting points that comprises a thin platecomposed of two intimately united portions of different conductingmaterials, constituting a thermo-electric couple, and modified inoutline to localize the applied heat at the junc-' tlon point of the twomaterials, means for supplying electric current to the said plate, anelectrical me suring instrument and means whereby tlie same is connectedto measure the potential generated by the said couple. I

7 A device for determining melting points that comprises a thin platecomposed of two portions of different conductingmaterials butt-weldedtogether and constituting a thermo-electric couple, the said couplebeing notched to localize the applied heat at,

the junction point of the two materials, means for supplying electriccurrent to the said plate, an electric measuring instrument, meanswhereby the same is connected to measure the energy generated by thesaid couple, and a holder for the said plate In testimony whereof Wehave hereunto subscribed our names this th day of April,

LEWIS W. CHUBB. ROBSON DE s. BROWN.

